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</pre><pre class="rust ">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">collections</span>::<span class="ident">HashMap</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">cmp</span>::<span class="ident">Ordering</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ops</span>::<span class="ident">Deref</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">mem</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">slice</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">Arc</span>;

<span class="kw">use</span> <span class="ident">input</span>::<span class="ident">Char</span>;
<span class="kw">use</span> <span class="ident">literals</span>::<span class="ident">LiteralSearcher</span>;

<span class="doccomment">/// InstPtr represents the index of an instruction in a regex program.</span>
<span class="kw">pub</span> <span class="kw">type</span> <span class="ident">InstPtr</span> <span class="op">=</span> <span class="ident">usize</span>;

<span class="doccomment">/// Program is a sequence of instructions and various facts about thos</span>
<span class="doccomment">/// instructions.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Program</span> {
    <span class="doccomment">/// A sequence of instructions that represents an NFA.</span>
    <span class="kw">pub</span> <span class="ident">insts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Inst</span><span class="op">&gt;</span>,
    <span class="doccomment">/// Pointers to each Match instruction in the sequence.</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// This is always length 1 unless this program represents a regex set.</span>
    <span class="kw">pub</span> <span class="ident">matches</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">InstPtr</span><span class="op">&gt;</span>,
    <span class="doccomment">/// The ordered sequence of all capture groups extracted from the AST.</span>
    <span class="doccomment">/// Unnamed groups are `None`.</span>
    <span class="kw">pub</span> <span class="ident">captures</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">String</span><span class="op">&gt;&gt;</span>,
    <span class="doccomment">/// Pointers to all named capture groups into `captures`.</span>
    <span class="kw">pub</span> <span class="ident">capture_name_idx</span>: <span class="ident">Arc</span><span class="op">&lt;</span><span class="ident">HashMap</span><span class="op">&lt;</span><span class="ident">String</span>, <span class="ident">usize</span><span class="op">&gt;&gt;</span>,
    <span class="doccomment">/// A pointer to the start instruction. This can vary depending on how</span>
    <span class="doccomment">/// the program was compiled. For example, programs for use with the DFA</span>
    <span class="doccomment">/// engine have a `.*?` inserted at the beginning of unanchored regular</span>
    <span class="doccomment">/// expressions. The actual starting point of the program is after the</span>
    <span class="doccomment">/// `.*?`.</span>
    <span class="kw">pub</span> <span class="ident">start</span>: <span class="ident">InstPtr</span>,
    <span class="doccomment">/// A set of equivalence classes for discriminating bytes in the compiled</span>
    <span class="doccomment">/// program.</span>
    <span class="kw">pub</span> <span class="ident">byte_classes</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">u8</span><span class="op">&gt;</span>,
    <span class="doccomment">/// When true, this program can only match valid UTF-8.</span>
    <span class="kw">pub</span> <span class="ident">only_utf8</span>: <span class="ident">bool</span>,
    <span class="doccomment">/// When true, this program uses byte range instructions instead of Unicode</span>
    <span class="doccomment">/// range instructions.</span>
    <span class="kw">pub</span> <span class="ident">is_bytes</span>: <span class="ident">bool</span>,
    <span class="doccomment">/// When true, the program is compiled for DFA matching. For example, this</span>
    <span class="doccomment">/// implies `is_bytes` and also inserts a preceding `.*?` for unanchored</span>
    <span class="doccomment">/// regexes.</span>
    <span class="kw">pub</span> <span class="ident">is_dfa</span>: <span class="ident">bool</span>,
    <span class="doccomment">/// When true, the program matches text in reverse (for use only in the</span>
    <span class="doccomment">/// DFA).</span>
    <span class="kw">pub</span> <span class="ident">is_reverse</span>: <span class="ident">bool</span>,
    <span class="doccomment">/// Whether the regex must match from the start of the input.</span>
    <span class="kw">pub</span> <span class="ident">is_anchored_start</span>: <span class="ident">bool</span>,
    <span class="doccomment">/// Whether the regex must match at the end of the input.</span>
    <span class="kw">pub</span> <span class="ident">is_anchored_end</span>: <span class="ident">bool</span>,
    <span class="doccomment">/// Whether this program contains a Unicode word boundary instruction.</span>
    <span class="kw">pub</span> <span class="ident">has_unicode_word_boundary</span>: <span class="ident">bool</span>,
    <span class="doccomment">/// A possibly empty machine for very quickly matching prefix literals.</span>
    <span class="kw">pub</span> <span class="ident">prefixes</span>: <span class="ident">LiteralSearcher</span>,
    <span class="doccomment">/// A limit on the size of the cache that the DFA is allowed to use while</span>
    <span class="doccomment">/// matching.</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// The cache limit specifies approximately how much space we&#39;re willing to</span>
    <span class="doccomment">/// give to the state cache. Once the state cache exceeds the size, it is</span>
    <span class="doccomment">/// wiped and all states must be re-computed.</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// Note that this value does not impact correctness. It can be set to 0</span>
    <span class="doccomment">/// and the DFA will run just fine. (It will only ever store exactly one</span>
    <span class="doccomment">/// state in the cache, and will likely run very slowly, but it will work.)</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// Also note that this limit is *per thread of execution*. That is,</span>
    <span class="doccomment">/// if the same regex is used to search text across multiple threads</span>
    <span class="doccomment">/// simultaneously, then the DFA cache is not shared. Instead, copies are</span>
    <span class="doccomment">/// made.</span>
    <span class="kw">pub</span> <span class="ident">dfa_size_limit</span>: <span class="ident">usize</span>,
}

<span class="kw">impl</span> <span class="ident">Program</span> {
    <span class="doccomment">/// Creates an empty instruction sequence. Fields are given default</span>
    <span class="doccomment">/// values.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-&gt;</span> <span class="self">Self</span> {
        <span class="ident">Program</span> {
            <span class="ident">insts</span>: <span class="macro">vec</span><span class="macro">!</span>[],
            <span class="ident">matches</span>: <span class="macro">vec</span><span class="macro">!</span>[],
            <span class="ident">captures</span>: <span class="macro">vec</span><span class="macro">!</span>[],
            <span class="ident">capture_name_idx</span>: <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">HashMap</span>::<span class="ident">new</span>()),
            <span class="ident">start</span>: <span class="number">0</span>,
            <span class="ident">byte_classes</span>: <span class="macro">vec</span><span class="macro">!</span>[<span class="number">0</span>; <span class="number">256</span>],
            <span class="ident">only_utf8</span>: <span class="bool-val">true</span>,
            <span class="ident">is_bytes</span>: <span class="bool-val">false</span>,
            <span class="ident">is_dfa</span>: <span class="bool-val">false</span>,
            <span class="ident">is_reverse</span>: <span class="bool-val">false</span>,
            <span class="ident">is_anchored_start</span>: <span class="bool-val">false</span>,
            <span class="ident">is_anchored_end</span>: <span class="bool-val">false</span>,
            <span class="ident">has_unicode_word_boundary</span>: <span class="bool-val">false</span>,
            <span class="ident">prefixes</span>: <span class="ident">LiteralSearcher</span>::<span class="ident">empty</span>(),
            <span class="ident">dfa_size_limit</span>: <span class="number">2</span> <span class="op">*</span> (<span class="number">1</span><span class="op">&lt;&lt;</span><span class="number">20</span>),
        }
    }

    <span class="doccomment">/// If pc is an index to a no-op instruction (like Save), then return the</span>
    <span class="doccomment">/// next pc that is not a no-op instruction.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">skip</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="kw-2">mut</span> <span class="ident">pc</span>: <span class="ident">usize</span>) <span class="op">-&gt;</span> <span class="ident">usize</span> {
        <span class="kw">loop</span> {
            <span class="kw">match</span> <span class="self">self</span>[<span class="ident">pc</span>] {
                <span class="ident">Inst</span>::<span class="ident">Save</span>(<span class="kw-2">ref</span> <span class="ident">i</span>) <span class="op">=&gt;</span> <span class="ident">pc</span> <span class="op">=</span> <span class="ident">i</span>.<span class="ident">goto</span>,
                _ <span class="op">=&gt;</span> <span class="kw">return</span> <span class="ident">pc</span>,
            }
        }
    }

    <span class="doccomment">/// Return true if and only if an execution engine at instruction `pc` will</span>
    <span class="doccomment">/// always lead to a match.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">leads_to_match</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">pc</span>: <span class="ident">usize</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">matches</span>.<span class="ident">len</span>() <span class="op">&gt;</span> <span class="number">1</span> {
            <span class="comment">// If we have a regex set, then we have more than one ending</span>
            <span class="comment">// state, so leading to one of those states is generally</span>
            <span class="comment">// meaningless.</span>
            <span class="kw">return</span> <span class="bool-val">false</span>;
        }
        <span class="kw">match</span> <span class="self">self</span>[<span class="self">self</span>.<span class="ident">skip</span>(<span class="ident">pc</span>)] {
            <span class="ident">Inst</span>::<span class="ident">Match</span>(_) <span class="op">=&gt;</span> <span class="bool-val">true</span>,
            _ <span class="op">=&gt;</span> <span class="bool-val">false</span>,
        }
    }

    <span class="doccomment">/// Returns true if the current configuration demands that an implicit</span>
    <span class="doccomment">/// `.*?` be prepended to the instruction sequence.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">needs_dotstar</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="self">self</span>.<span class="ident">is_dfa</span> <span class="op">&amp;&amp;</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">is_reverse</span> <span class="op">&amp;&amp;</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">is_anchored_start</span>
    }

    <span class="doccomment">/// Returns true if this program uses Byte instructions instead of</span>
    <span class="doccomment">/// Char/Range instructions.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">uses_bytes</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="self">self</span>.<span class="ident">is_bytes</span> <span class="op">||</span> <span class="self">self</span>.<span class="ident">is_dfa</span>
    }

    <span class="doccomment">/// Returns true if this program exclusively matches valid UTF-8 bytes.</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// That is, if an invalid UTF-8 byte is seen, then no match is possible.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">only_utf8</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="self">self</span>.<span class="ident">only_utf8</span>
    }

    <span class="doccomment">/// Return the approximate heap usage of this instruction sequence in</span>
    <span class="doccomment">/// bytes.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">approximate_size</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">usize</span> {
        <span class="comment">// The only instruction that uses heap space is Ranges (for</span>
        <span class="comment">// Unicode codepoint programs) to store non-overlapping codepoint</span>
        <span class="comment">// ranges. To keep this operation constant time, we ignore them.</span>
        (<span class="self">self</span>.<span class="ident">len</span>() <span class="op">*</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op">&lt;</span><span class="ident">Inst</span><span class="op">&gt;</span>())
        <span class="op">+</span> (<span class="self">self</span>.<span class="ident">matches</span>.<span class="ident">len</span>() <span class="op">*</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op">&lt;</span><span class="ident">InstPtr</span><span class="op">&gt;</span>())
        <span class="op">+</span> (<span class="self">self</span>.<span class="ident">captures</span>.<span class="ident">len</span>() <span class="op">*</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op">&lt;</span><span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">String</span><span class="op">&gt;&gt;</span>())
        <span class="op">+</span> (<span class="self">self</span>.<span class="ident">capture_name_idx</span>.<span class="ident">len</span>() <span class="op">*</span>
           (<span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op">&lt;</span><span class="ident">String</span><span class="op">&gt;</span>() <span class="op">+</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op">&lt;</span><span class="ident">usize</span><span class="op">&gt;</span>()))
        <span class="op">+</span> (<span class="self">self</span>.<span class="ident">byte_classes</span>.<span class="ident">len</span>() <span class="op">*</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op">&lt;</span><span class="ident">u8</span><span class="op">&gt;</span>())
        <span class="op">+</span> <span class="self">self</span>.<span class="ident">prefixes</span>.<span class="ident">approximate_size</span>()
    }
}

<span class="kw">impl</span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="ident">Program</span> {
    <span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> [<span class="ident">Inst</span>];

    <span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="kw-2">&amp;</span><span class="self">Self</span>::<span class="ident">Target</span> {
        <span class="kw-2">&amp;</span><span class="kw-2">*</span><span class="self">self</span>.<span class="ident">insts</span>
    }
}

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Program</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="kw">use</span> <span class="self">self</span>::<span class="ident">Inst</span>::<span class="kw-2">*</span>;

        <span class="kw">fn</span> <span class="ident">with_goto</span>(<span class="ident">cur</span>: <span class="ident">usize</span>, <span class="ident">goto</span>: <span class="ident">usize</span>, <span class="ident">fmtd</span>: <span class="ident">String</span>) <span class="op">-&gt;</span> <span class="ident">String</span> {
            <span class="kw">if</span> <span class="ident">goto</span> <span class="op">==</span> <span class="ident">cur</span> <span class="op">+</span> <span class="number">1</span> {
                <span class="ident">fmtd</span>
            } <span class="kw">else</span> {
                <span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{} (goto: {})&quot;</span>, <span class="ident">fmtd</span>, <span class="ident">goto</span>)
            }
        }

        <span class="kw">fn</span> <span class="ident">visible_byte</span>(<span class="ident">b</span>: <span class="ident">u8</span>) <span class="op">-&gt;</span> <span class="ident">String</span> {
            <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ascii</span>::<span class="ident">escape_default</span>;
            <span class="kw">let</span> <span class="ident">escaped</span> <span class="op">=</span> <span class="ident">escape_default</span>(<span class="ident">b</span>).<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">u8</span><span class="op">&gt;&gt;</span>();
            <span class="ident">String</span>::<span class="ident">from_utf8_lossy</span>(<span class="kw-2">&amp;</span><span class="ident">escaped</span>).<span class="ident">into_owned</span>()
        }

        <span class="kw">for</span> (<span class="ident">pc</span>, <span class="ident">inst</span>) <span class="kw">in</span> <span class="self">self</span>.<span class="ident">iter</span>().<span class="ident">enumerate</span>() {
            <span class="kw">match</span> <span class="kw-2">*</span><span class="ident">inst</span> {
                <span class="ident">Match</span>(<span class="ident">slot</span>) <span class="op">=&gt;</span> {
                    <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot;{:04} Match({:?})&quot;</span>, <span class="ident">pc</span>, <span class="ident">slot</span>))
                }
                <span class="ident">Save</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=&gt;</span> {
                    <span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:04} Save({})&quot;</span>, <span class="ident">pc</span>, <span class="ident">inst</span>.<span class="ident">slot</span>);
                    <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot;{}&quot;</span>, <span class="ident">with_goto</span>(<span class="ident">pc</span>, <span class="ident">inst</span>.<span class="ident">goto</span>, <span class="ident">s</span>)));
                }
                <span class="ident">Split</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=&gt;</span> {
                    <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot;{:04} Split({}, {})&quot;</span>,
                                <span class="ident">pc</span>, <span class="ident">inst</span>.<span class="ident">goto1</span>, <span class="ident">inst</span>.<span class="ident">goto2</span>));
                }
                <span class="ident">EmptyLook</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=&gt;</span> {
                    <span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">inst</span>.<span class="ident">look</span>);
                    <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot;{:04} {}&quot;</span>,
                                <span class="ident">pc</span>, <span class="ident">with_goto</span>(<span class="ident">pc</span>, <span class="ident">inst</span>.<span class="ident">goto</span>, <span class="ident">s</span>)));
                }
                <span class="ident">Char</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=&gt;</span> {
                    <span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">inst</span>.<span class="ident">c</span>);
                    <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot;{:04} {}&quot;</span>,
                                <span class="ident">pc</span>, <span class="ident">with_goto</span>(<span class="ident">pc</span>, <span class="ident">inst</span>.<span class="ident">goto</span>, <span class="ident">s</span>)));
                }
                <span class="ident">Ranges</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=&gt;</span> {
                    <span class="kw">let</span> <span class="ident">ranges</span> <span class="op">=</span> <span class="ident">inst</span>.<span class="ident">ranges</span>
                        .<span class="ident">iter</span>()
                        .<span class="ident">map</span>(<span class="op">|</span><span class="ident">r</span><span class="op">|</span> <span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:?}-{:?}&quot;</span>, <span class="ident">r</span>.<span class="number">0</span>, <span class="ident">r</span>.<span class="number">1</span>))
                        .<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">String</span><span class="op">&gt;&gt;</span>()
                        .<span class="ident">join</span>(<span class="string">&quot;, &quot;</span>);
                    <span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{}&quot;</span>, <span class="ident">ranges</span>);
                    <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot;{:04} {}&quot;</span>,
                                <span class="ident">pc</span>, <span class="ident">with_goto</span>(<span class="ident">pc</span>, <span class="ident">inst</span>.<span class="ident">goto</span>, <span class="ident">s</span>)));
                }
                <span class="ident">Bytes</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=&gt;</span> {
                    <span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="macro">format</span><span class="macro">!</span>(
                        <span class="string">&quot;Bytes({}, {})&quot;</span>,
                        <span class="ident">visible_byte</span>(<span class="ident">inst</span>.<span class="ident">start</span>),
                        <span class="ident">visible_byte</span>(<span class="ident">inst</span>.<span class="ident">end</span>));
                    <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot;{:04} {}&quot;</span>,
                                <span class="ident">pc</span>, <span class="ident">with_goto</span>(<span class="ident">pc</span>, <span class="ident">inst</span>.<span class="ident">goto</span>, <span class="ident">s</span>)));
                }
            }
            <span class="kw">if</span> <span class="ident">pc</span> <span class="op">==</span> <span class="self">self</span>.<span class="ident">start</span> {
                <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot; (start)&quot;</span>));
            }
            <span class="macro">try</span><span class="macro">!</span>(<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">&quot;\n&quot;</span>));
        }
        <span class="prelude-val">Ok</span>(())
    }
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="lifetime">&#39;a</span><span class="op">&gt;</span> <span class="ident">IntoIterator</span> <span class="kw">for</span> <span class="kw-2">&amp;</span><span class="lifetime">&#39;a</span> <span class="ident">Program</span> {
    <span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="lifetime">&#39;a</span> <span class="ident">Inst</span>;
    <span class="kw">type</span> <span class="ident">IntoIter</span> <span class="op">=</span> <span class="ident">slice</span>::<span class="ident">Iter</span><span class="op">&lt;</span><span class="lifetime">&#39;a</span>, <span class="ident">Inst</span><span class="op">&gt;</span>;
    <span class="kw">fn</span> <span class="ident">into_iter</span>(<span class="self">self</span>) <span class="op">-&gt;</span> <span class="self">Self</span>::<span class="ident">IntoIter</span> { <span class="self">self</span>.<span class="ident">iter</span>() }
}

<span class="doccomment">/// Inst is an instruction code in a Regex program.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Regrettably, a regex program either contains Unicode codepoint</span>
<span class="doccomment">/// instructions (Char and Ranges) or it contains byte instructions (Bytes).</span>
<span class="doccomment">/// A regex program can never contain both.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It would be worth investigating splitting this into two distinct types and</span>
<span class="doccomment">/// then figuring out how to make the matching engines polymorphic over those</span>
<span class="doccomment">/// types without sacrificing performance.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Other than the benefit of moving invariants into the type system, another</span>
<span class="doccomment">/// benefit is the decreased size. If we remove the `Char` and `Ranges`</span>
<span class="doccomment">/// instructions from the `Inst` enum, then its size shrinks from 40 bytes to</span>
<span class="doccomment">/// 24 bytes. (This is because of the removal of a `Vec` in the `Ranges`</span>
<span class="doccomment">/// variant.) Given that byte based machines are typically much bigger than</span>
<span class="doccomment">/// their Unicode analogues (because they can decode UTF-8 directly), this ends</span>
<span class="doccomment">/// up being a pretty significant savings.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">Inst</span> {
    <span class="doccomment">/// Match indicates that the program has reached a match state.</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// The number in the match corresponds to the Nth logical regular</span>
    <span class="doccomment">/// expression in this program. This index is always 0 for normal regex</span>
    <span class="doccomment">/// programs. Values greater than 0 appear when compiling regex sets, and</span>
    <span class="doccomment">/// each match instruction gets its own unique value. The value corresponds</span>
    <span class="doccomment">/// to the Nth regex in the set.</span>
    <span class="ident">Match</span>(<span class="ident">usize</span>),
    <span class="doccomment">/// Save causes the program to save the current location of the input in</span>
    <span class="doccomment">/// the slot indicated by InstSave.</span>
    <span class="ident">Save</span>(<span class="ident">InstSave</span>),
    <span class="doccomment">/// Split causes the program to diverge to one of two paths in the</span>
    <span class="doccomment">/// program, preferring goto1 in InstSplit.</span>
    <span class="ident">Split</span>(<span class="ident">InstSplit</span>),
    <span class="doccomment">/// EmptyLook represents a zero-width assertion in a regex program. A</span>
    <span class="doccomment">/// zero-width assertion does not consume any of the input text.</span>
    <span class="ident">EmptyLook</span>(<span class="ident">InstEmptyLook</span>),
    <span class="doccomment">/// Char requires the regex program to match the character in InstChar at</span>
    <span class="doccomment">/// the current position in the input.</span>
    <span class="ident">Char</span>(<span class="ident">InstChar</span>),
    <span class="doccomment">/// Ranges requires the regex program to match the character at the current</span>
    <span class="doccomment">/// position in the input with one of the ranges specified in InstRanges.</span>
    <span class="ident">Ranges</span>(<span class="ident">InstRanges</span>),
    <span class="doccomment">/// Bytes is like Ranges, except it expresses a single byte range. It is</span>
    <span class="doccomment">/// used in conjunction with Split instructions to implement multi-byte</span>
    <span class="doccomment">/// character classes.</span>
    <span class="ident">Bytes</span>(<span class="ident">InstBytes</span>),
}

<span class="kw">impl</span> <span class="ident">Inst</span> {
    <span class="doccomment">/// Returns true if and only if this is a match instruction.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_match</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
            <span class="ident">Inst</span>::<span class="ident">Match</span>(_) <span class="op">=&gt;</span> <span class="bool-val">true</span>,
            _ <span class="op">=&gt;</span> <span class="bool-val">false</span>,
        }
    }
}

<span class="doccomment">/// Representation of the Save instruction.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">InstSave</span> {
    <span class="doccomment">/// The next location to execute in the program.</span>
    <span class="kw">pub</span> <span class="ident">goto</span>: <span class="ident">InstPtr</span>,
    <span class="doccomment">/// The capture slot (there are two slots for every capture in a regex,</span>
    <span class="doccomment">/// including the zeroth capture for the entire match).</span>
    <span class="kw">pub</span> <span class="ident">slot</span>: <span class="ident">usize</span>,
}

<span class="doccomment">/// Representation of the Split instruction.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">InstSplit</span> {
    <span class="doccomment">/// The first instruction to try. A match resulting from following goto1</span>
    <span class="doccomment">/// has precedence over a match resulting from following goto2.</span>
    <span class="kw">pub</span> <span class="ident">goto1</span>: <span class="ident">InstPtr</span>,
    <span class="doccomment">/// The second instruction to try. A match resulting from following goto1</span>
    <span class="doccomment">/// has precedence over a match resulting from following goto2.</span>
    <span class="kw">pub</span> <span class="ident">goto2</span>: <span class="ident">InstPtr</span>,
}

<span class="doccomment">/// Representation of the EmptyLook instruction.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">InstEmptyLook</span> {
    <span class="doccomment">/// The next location to execute in the program if this instruction</span>
    <span class="doccomment">/// succeeds.</span>
    <span class="kw">pub</span> <span class="ident">goto</span>: <span class="ident">InstPtr</span>,
    <span class="doccomment">/// The type of zero-width assertion to check.</span>
    <span class="kw">pub</span> <span class="ident">look</span>: <span class="ident">EmptyLook</span>,
}

<span class="doccomment">/// The set of zero-width match instructions.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Debug</span>, <span class="ident">PartialEq</span>, <span class="ident">Eq</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">EmptyLook</span> {
    <span class="doccomment">/// Start of line or input.</span>
    <span class="ident">StartLine</span>,
    <span class="doccomment">/// End of line or input.</span>
    <span class="ident">EndLine</span>,
    <span class="doccomment">/// Start of input.</span>
    <span class="ident">StartText</span>,
    <span class="doccomment">/// End of input.</span>
    <span class="ident">EndText</span>,
    <span class="doccomment">/// Word character on one side and non-word character on other.</span>
    <span class="ident">WordBoundary</span>,
    <span class="doccomment">/// Word character on both sides or non-word character on both sides.</span>
    <span class="ident">NotWordBoundary</span>,
    <span class="doccomment">/// ASCII word boundary.</span>
    <span class="ident">WordBoundaryAscii</span>,
    <span class="doccomment">/// Not ASCII word boundary.</span>
    <span class="ident">NotWordBoundaryAscii</span>,
}

<span class="doccomment">/// Representation of the Char instruction.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">InstChar</span> {
    <span class="doccomment">/// The next location to execute in the program if this instruction</span>
    <span class="doccomment">/// succeeds.</span>
    <span class="kw">pub</span> <span class="ident">goto</span>: <span class="ident">InstPtr</span>,
    <span class="doccomment">/// The character to test.</span>
    <span class="kw">pub</span> <span class="ident">c</span>: <span class="ident">char</span>,
}

<span class="doccomment">/// Representation of the Ranges instruction.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">InstRanges</span> {
    <span class="doccomment">/// The next location to execute in the program if this instruction</span>
    <span class="doccomment">/// succeeds.</span>
    <span class="kw">pub</span> <span class="ident">goto</span>: <span class="ident">InstPtr</span>,
    <span class="doccomment">/// The set of Unicode scalar value ranges to test.</span>
    <span class="kw">pub</span> <span class="ident">ranges</span>: <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">char</span>, <span class="ident">char</span>)<span class="op">&gt;</span>,
}

<span class="kw">impl</span> <span class="ident">InstRanges</span> {
    <span class="doccomment">/// Tests whether the given input character matches this instruction.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">matches</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">c</span>: <span class="ident">Char</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="comment">// This speeds up the `match_class_unicode` benchmark by checking</span>
        <span class="comment">// some common cases quickly without binary search. e.g., Matching</span>
        <span class="comment">// a Unicode class on predominantly ASCII text.</span>
        <span class="kw">for</span> <span class="ident">r</span> <span class="kw">in</span> <span class="self">self</span>.<span class="ident">ranges</span>.<span class="ident">iter</span>().<span class="ident">take</span>(<span class="number">4</span>) {
            <span class="kw">if</span> <span class="ident">c</span> <span class="op">&lt;</span> <span class="ident">r</span>.<span class="number">0</span> {
                <span class="kw">return</span> <span class="bool-val">false</span>;
            }
            <span class="kw">if</span> <span class="ident">c</span> <span class="op">&lt;=</span> <span class="ident">r</span>.<span class="number">1</span> {
                <span class="kw">return</span> <span class="bool-val">true</span>;
            }
        }
        <span class="self">self</span>.<span class="ident">ranges</span>.<span class="ident">binary_search_by</span>(<span class="op">|</span><span class="ident">r</span><span class="op">|</span> {
            <span class="kw">if</span> <span class="ident">r</span>.<span class="number">1</span> <span class="op">&lt;</span> <span class="ident">c</span> {
                <span class="ident">Ordering</span>::<span class="ident">Less</span>
            } <span class="kw">else</span> <span class="kw">if</span> <span class="ident">r</span>.<span class="number">0</span> <span class="op">&gt;</span> <span class="ident">c</span> {
                <span class="ident">Ordering</span>::<span class="ident">Greater</span>
            } <span class="kw">else</span> {
                <span class="ident">Ordering</span>::<span class="ident">Equal</span>
            }
        }).<span class="ident">is_ok</span>()
    }

    <span class="doccomment">/// Return the number of distinct characters represented by all of the</span>
    <span class="doccomment">/// ranges.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">num_chars</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">usize</span> {
        <span class="self">self</span>.<span class="ident">ranges</span>.<span class="ident">iter</span>()
            .<span class="ident">map</span>(<span class="op">|</span><span class="kw-2">&amp;</span>(<span class="ident">s</span>, <span class="ident">e</span>)<span class="op">|</span> <span class="number">1</span> <span class="op">+</span> (<span class="ident">e</span> <span class="kw">as</span> <span class="ident">u32</span>) <span class="op">-</span> (<span class="ident">s</span> <span class="kw">as</span> <span class="ident">u32</span>))
            .<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">len</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">len</span>)
            <span class="kw">as</span> <span class="ident">usize</span>
    }
}

<span class="doccomment">/// Representation of the Bytes instruction.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">InstBytes</span> {
    <span class="doccomment">/// The next location to execute in the program if this instruction</span>
    <span class="doccomment">/// succeeds.</span>
    <span class="kw">pub</span> <span class="ident">goto</span>: <span class="ident">InstPtr</span>,
    <span class="doccomment">/// The start (inclusive) of this byte range.</span>
    <span class="kw">pub</span> <span class="ident">start</span>: <span class="ident">u8</span>,
    <span class="doccomment">/// The end (inclusive) of this byte range.</span>
    <span class="kw">pub</span> <span class="ident">end</span>: <span class="ident">u8</span>,
}

<span class="kw">impl</span> <span class="ident">InstBytes</span> {
    <span class="doccomment">/// Returns true if and only if the given byte is in this range.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">matches</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">byte</span>: <span class="ident">u8</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="self">self</span>.<span class="ident">start</span> <span class="op">&lt;=</span> <span class="ident">byte</span> <span class="op">&amp;&amp;</span> <span class="ident">byte</span> <span class="op">&lt;=</span> <span class="self">self</span>.<span class="ident">end</span>
    }
}
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